4 NATICID^. 201 



Tychonia, de Koninck, 1881. 



Distr. — T. Omaliana^ de Kon. Carboniferous; Belgium. 



Shell somewhat depressed, globular, smooth ; spire short, 

 obtuse, sutures shallow ; last whorl very large ; mouth semicir- 

 cular, outer lip sharp, inner lip somewhat calloiTS ; an umbilical 

 fissure. 



SiGARETUS, Lam. 



Syn. — Catinus (Klein), H. and A. Adams. Lupia, Conr. 

 Stomatia, Hill. Raynevallia, Ponzi. 



Distr. — 90 recent sp. United States, West Indies, China, 

 Peru. Fossil, 10 sp. Eocene — . S. neritoideus, Linn. (Ixiii, 

 52). 



Shell ear-shaped, with minute spire and very large aperture, 

 externally with revolving striae, color usuall}^ white, with some- 

 times a thin corneous epidermis. Operculum minute, horny, 

 subspiral. Animal with large mantle partly or entirely covering 

 the shell, anterior foot-lobe enormously developed. 



They live on muddy sand-flats ; in their habits they are 

 sluggish and slow-moving, and very timid ; when crawling they 

 constantly explore the surrounding surface with the produced 

 fore-lobe of the foot, which is also used in burrowing. 



SIGARETUS, Lam. (typical). Shell orbicular, conoidal or convex ; 

 mouth rounded ; umbilicus open or covered by a reflection of the 

 inner lip ; spire short, oblique. 



NATiciNA, Gra}'. (Lacunaria, Conr.) Shell oval-oblong, thin, 

 ventricose ; spire sharp ; inner lip straight, thin anteriorly, with 

 a median callus ; umbilicus open or parti}' covered. S. papilla, 

 Gmel. (Ixiii, 53). 



CRYPTOSTOMA, Blalnv. Shell ear-shaped, flattened; spire short, 

 depressed ; mouth very large, oblique ; no umbilicus. S. halio- 

 toides, Linn. (Ixiii, 54). 



Velutina, Fleming. 



Etym. — Velutinus, velvety (from vellus, a fleece). 



Syn. — (?) Catinella, Stache. 



Distr. — 4 sp. Boreal Seas, Europe and America. Fossil. 

 Triassic, Cretaceous, Pliocene — . V. capuloidea, Blainv. (Ixiii, 

 55). V. Isevigata, Linn. (Ixiii, 56). 



Shell thin, with a velvety epidermis ; spire small, sutures well- 

 impressed ; aperture very large, rounded ; peristome continuous, 

 thin. No operculum. 



Animal with a large oblong foot ; margin of the mantle 

 developed all around, and more or less reflected over the shell ; 

 head broad ; tentacles subulate, blunt, far apart, with eyes on 

 prominences at their outer bases. 



The Yelutinas, although resembling the pulmoniferous genus 

 Otina, are strictly marine, being met with sometimes far out at 



